As a kind of semiconductor devices, a three-dimensional NAND-type flash memory device has been known. In manufacturing the three-dimensional NAND-type flash memory device, etching is performed on a multilayer film configured by alternately providing two layers having different dielectric constants to form a deep hole in the multilayer film. Such etching is disclosed in U.S. Patent Application Publication No. 2013/0059450.
Specifically, U.S. Patent Application Publication No. 2013/0059450 discloses that an object to be processed (“workpiece”) having a mask made of amorphous silicon on a multilayer film is exposed to plasma of a processing gas including CH2F2 gas, N2 gas, and NF3 gas, thereby etching the multilayer film.